4.1 adds a new arg, hideCaster (boolean), and of course, with blizz tradition, not at the end, but right smack in the middle offseting rest of args and breaking mods not updated to account for it. This boolean isn't logged by /combatlog so that parsing seems unaffected.

To perhaps help explain why it's in the middle instead of the end... The different CLEU events add returns to the end of the normal CLEU returns.

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"You'd be surprised how many people violate this simple principle every day of their lives and try to fit square pegs into round holes, ignoring the clear reality that Things Are As They Are." -Benjamin Hoff, The Tao of Pooh

When trying to make mods compatible between 4.0.6 and 4.1 I noticed that GetBuildInfo() is still returning 40000 as its 4th value on the PTR, even though the 1st value is "4.1.0". I resorted to this for consistency's sake: